Now there's Two

In the penultimate battle, rely on your heavy hitting ammo such as boombats or stingbees and thudslugs. Make sure to get out of their goo quickly if you are hit by it. If they get close to you they'll start spinning which does heavy damage, but don't run away because they will manage to stop you quickly. Instead, start firing on them and eventually they will teleport to the other side of the room.